The present invention relates to improvements in methods and systems for controlling material processing operations such as mixing, separation, maintenance, and material analysis. Such improvements are applicable to industrial plants such as chemical plants, power plants, oil refineries as well as to specialized material processing or analysis equipment such as chemical analyzers.
A common method for separating out heavier components from a liquid mixture is the use of centrifugation, whereby the mixture is subjected to a centrifugal force field which causes the sedimentation of the components at different rates according to their densities and volumes. In a centrifuge for separating biological cells, for example, a suspension of cells in a liquid medium is placed in a centrifuge tube which is rotated rapidly about an axis some distance from the tube so as to cause sedimentation of the cells and other structures toward the bottom of the tube. Cells or other particles may thus be separated differentially by varying the time of centrifugation with the denser components settling at the bottom of the tube first. Such differential centrifugation is commonly used, for example, to separate red blood cells from white blood cells owing to the greater density of the former. After disruption of cells into a heterogeneous liquid, centrifugation is also used to separate cellular constituent parts such as nuclei, mitochondria, ribosomes, etc.
Any heterogeneous liquid mixture may be subjected to centrifugation. A more clearly demarcated degree of separation may be achieved, however, by interposing a density barrier which only particles having a greater density may penetrate. For example, a blood cell suspension may be layered over a solution of albumin or sucrose whose density is between that of red and white cells, allowing the red cells but not the white cells to go through the density barrier which affords a better separation. Modifications of this technique, called density gradient centrifugation, include using a centrifuge medium having a number of layers of varying density or using a medium having a continuous density gradient along the length of the centrifuge tube. If the different densities of the medium encompass the range of densities represented by the different components desired to be separated, each component will come to rest in a layer of the medium whose density matches its own.
Centrifugation may also be used in a continuous flow process in which heavier or lighter components are removed from a feedstock. Centrifugal separators of this type are commonly used in the dairy and paper industries as well as in isotopic separation processes. Since the liquid which is centrifuged in these cases is the feedstock itself and not a special centrifugation medium, it is usually not possible to employ the density gradient technique as described above to enhance the degree of separation of the components. A cleaner separation may be achieved, however, by the use of multi-stage centrifugal separators in which the feedstock is continuously depleted of either the heavier or lighter components as it proceeds through the multiple stages.
In any of the centrifugal separation processes described above, it would be advantageous if the centrifuge could be operated so as to optimize the separation of a select component or components from the rest of the mixture. For example, in density gradient centrifugation, the centrifugation must proceed long enough for the different particles to localize in their individual density layers. How long this takes depends on the sedimentation constants of the particles, the rotational speed of the centrifuge, and the composition of the centrifuge medium. If the centrifugation is allowed to proceed for too long and at too high a speed, however, disruption of the desired layers as well as fragile components such as cells may occur. In accordance with the present invention, therefore, a quantity of detectable test particles having a sedimentation constant approximately equal to that of a select component of a mixture which it is desired to separate is added to the mixture before or during the centrifugation. Such test particles, depending upon the type of mixture component whose sedimentation rate they are designed to emulate, may be either molecules or larger particles to which is conjugated a tag enabling the test particle to be detected by electro-optical or other means. The position and/or velocity of the test particles in the mixture as centrifugation proceeds is monitored by a scanning device which feeds the position data to a computer which then controls the speed and duration of the centrifuge so as to result in a desired localization of the component which it is desired to separate. By means of such adaptive control of the centrifuge, its operation may be optimized to separate out a select component even as the composition of the centrifuge medium varies. The technique is thus especially useful in those applications where centrifugation takes place in a native medium subject to a great deal of variability as opposed to an artificial centrifuge medium.
The present invention may also be used in continuous centrifugal separation operations to control the speed of each of the individual centrifugal separation stages so as to result in the optimum separation of a select component or components from the feedstock. Other variables which may also be controlled include impeller blade angles and rate of throughput into each stage. In a continuous separation operation, test particles are continuously added to the feedstock, and the concentration of the particles is continuously monitored in the product coming out of the separator. A plurality of different test particles may also be used with each having a sedimentation constant corresponding to a different component of the feedstock. Select components may then be optimally stripped from the feedstock by removing product from select stages and operating the stages in accordance with the concentration of test particles in each product stream. In cases where it is desired to remove the test particles from the product, the particles may be composed or partly composed of a ligand having a binding affinity for specific molecules immobilized in a reaction column. The test particles may then be separated from the rest of the product by passing the product through the reaction column.
Mixing is a common operation that effects the distribution, intermingling, and homogeneity of matter and is almost always accomplished by agitation of the matter components to be mixed. Other processes, such as chemical reaction, mass transfer (including solubility and crystallization), heat transfer, and dispersion, are also promoted by agitation. The type, extent, and intensity of agitation determine both the rates and adequacy of a particular process result. Agitation may be performed by different types of equipment, but most liquid mixing is done by rotating impellers in cylindrical vessels. A typical impeller-type liquid mixer includes a vessel, an impeller and a plurality of side mounted baffles. The forces applied by the impeller develop circulation or bulk flow within the matter to be mixed. Superimposed on this flow pattern is molecular diffusion, and if turbulence is present, turbulent eddies, both of which provide intermingling of the component particles at a micro level.
Bulk circulation results when the fluid stream is discharged by the impeller, while turbulence is generated mostly by the velocity discontinuities adjacent to the stream of fluid flowing from the impeller. Turbulence spreads throughout the bulk flow and, although attenuated, is carried to all parts of the vessel. It is recognized that some mixing operations require relatively large bulk flows, whereas others need a high degree of turbulence. It follows therefore that there is an optimum ratio of flow to turbulence for any particular mixing operation. Kinetic energy imparted to the fluid by the mixing impeller produces both bulk flow and turbulence, with a high rotational speed tending to produce more turbulence and a large diameter tending to produce more bulk flow. Impeller shape also has an effect which can be significant, with a rotating disk representing the extreme case for producing high turbulence. The ratio of bulk flow to turbulence also depends on the shape of the mixing vessel; the fittings it contains; the type, size, and position of the impeller; and, of course, the properties of the fluid. Radial and vertical flow currents penetrating to all portions of the fluid usually produce the best mixing. Vertical baffles are commonly provided to effect such flow patterns for impellers which are centrally located, while they may be omitted if an impeller used in an off-center position.
Mixing impellers may be of several types (such as a marine-type propeller, a pitched-blade turbine, or a flat paddle wheel), but any of them centrally positioned produce rotating fluid motion with a vortex around which liquid swirls. This motion constitutes bulk flow but often results in separation or stratification rather than intermingling. The result is little turbulence and only a small amount of vertical and lateral flow motion. Inserting projections into the body of the fluid (ie., baffles) stops the rotary motion, and the vortex disappears, thus improving the mixing. FIG. 2 shows the the desireable vertical and lateral flow patterns produced by a centrally located impeller in a mixing vessel having baffles from the side and bottom, respectively.
It is possible, of course, to design a mixing apparatus for a particular process involving the mixing of particular components under specified conditions that produces an optimal ratio of turbulence to bulk flow. It would be desirable, however, if a mixing apparatus could be provided which is capable of adapting to different process conditions (such as different material components) by dynamically adjusting mixing variables in a manner which optimizes the mixing.
One aspect of the present invention relates to a system and method for mixing fluent materials, such as solid or liquid particles, liquids, viscous solids or liquids, or combinations thereof, under the control of a computer. In particular, the invention involves sensing and scanning techniques for scanning materials as they are mixed and generating feedback signals which are computer processed and analyzed to generate control signals wherein such control signals are employed to control and vary accordingly one or more mixing process variables to optimize and/or enhance the mixing operation. In one particular form of the invention, a machine vision system or systems are employed to electro-optically detect such variables as the colors or densities of two or more materials being mixed, the shape or shapes of solid or liquid particles at one or more time during the mixing operation, and/or flow patterns occurring within the mixing vessel. Such optical variables may be detected and quantized by employing one or more television cameras, photoelectric scanning systems, and/or radiation generated by one or more lasers.
In one form of the invention, a single television camera is positioned to scan the surface of mixing materials during the mixing operation and the resulting video signals are computer processed and analyzed by comparing the results of processing with image information, such as codes, derived from memory. The mixing operation may be terminated by signals generated by the computer when it electronically recognizes that the mixed material has a color, shade or variations thereof which indicate, by signal comparison or other means, that mixing is complete.
In another form, a laser beam is caused to intersect while directed without scanning, a select portion of the surface of the mixing material and/or to scan same in a select path whereupon the reflected light of the laser beam and/or spectral light energy generated by one or more of the mixing materials, is photoelectrically detected by one or more photoelectric cells and/or by solid state detection elements or a television camera. The scanning and detection process continues during the mixing operation and the resulting image signals are computer processed and analyzed in a manner to detect when mixing is complete and, in certain instances, when mixing is taking place incorrectly. The resulting coded electrical signals are employed to control and/or terminate the mixing operation. Such control may be effected in a number of ways including controlling one or more motors rotating one or more mixing assemblies, such as blades, turbines or other mixing devices; control of one or more valves and/or motors which pump or otherwise affect the flow of one or more of the fluent materials being mixed; control of radiation applied to the mixing materials; control of one or more ultrasonic energy generating transducers employed in mixing; control of pressure in the mixing chamber, or control of other process variables affecting the mixing process. Fuzzy logic and neural networks electronic hardware and software may be employed in the computer analysis of the image information derived from scanning the surface or surfaces of the mixing materials and, in certain instances, from image information derived from one or more electro-optical scanners scanning reflections of laser light within the mixing fluids wherein such electro-optical scanners are disposed within one or more tubes extending into the mixing materials and/or supported by the mixing blades or a portion of the mixer assembly.
Another aspect of the invention relates to a system and method for performing experiments and diagnostic tests, such as relating to chemistry, medicine and other areas of technology involving systematic procedures and steps which may be computer controlled and wherein results of the experiments or analyses may be electronically detected, processed and analyzed. In particular, the invention is concerned with such an experimentation or test system and method wherein a computer is utilized to control experiments and tests, determine and analyze results, and make decisions with respect to additional or future experiments and tests without the need for human attendance, analysis or decision-making. In one form, a digital computer is programmed to receive and analyze data generated by sensors which sense and detect variations in matter, such a chemicals or living tissue, as an experiment progresses and which analyze and generate electrical signals indicative of the results of the experiment. Such electrical signals are compared with signals generated from recordings in a memory and are processed therewith to generate additional control signals for effecting either continuation of the experiment or the performance of an additional experiment or experiments with respect to the chemicals or living matter which has been generated or affected by the prior experiment. This process is repeated a number of times, either until a desired result has been obtained or a number of steps has been effected wherein a previously unknown result has occurred and may be indicated by sensing such result. In a particular form, the system includes supplies of a variety of different materials and means for controllably dispensing or carrying such materials to selective locations within the system and/or to or within a specimen being subjected to test of experimentation. By utilizing such a system and method involving the computer control of one or more simultaneously and/or consecutively conducted experiments with computer analysis of results to determine future experiments to be performed, experimental procedure may be substantially improved by eliminating unnecessary testing and reducing the time required to perform one or a series of experiments.
Another aspect of the present invention relates to an apparatus and method for automatically inspecting, maintaining, repairing, assembling and/or cleaning containers such as large storage tanks. Storage devices, such as large cylindrical tanks, are employed in many industries including the chemical, drug and biological industries to store a variety of fluent materials and solids contained in liquids, and, in certain instances, to permit the processing of matter within the tanks, wherein contamination may periodically take place requiring that the tanks be emptied or reduced in contents and cleaned. Heretofore, such tanks must be emptied and taken out of service before any cleaning, repairing, or inspecting of the tank's inner walls can be undertaken. The cleaning operation is generally performed by one or more human beings with brushes, hoses and nozzles for cleaning liquids steam and the like, operable to remove contaminants from the inside surfaces of the side walls and bottoms of the tanks.
In accordance with the invention, disposed within a tank is an automatic manipulator having one or more operating heads for containing one or more devices such as spray nozzles, brushes, and inspection or handling devices. The operating head(s) is attached to a manipulator arm which extends laterally from a rotor assembly so that the operating head engages an inner wall surface of the tank. The rotor assembly is disposed so as to be rotatable about a central axis of the tank, and the manipulator arm is mounted to the rotor assembly so as to be vertically adjustable with respect thereto. By power rotating the rotor assembly, the operating head is made to scan the inner wall surface of the tank in circular fashion and operate thereon. By vertically adjusting the elevation of the manipulator arm with respect to the rotor assembly during such scanning, the operating head is caused to scan the inner wall surface of the tank either in a spiral manner or in a stepped series of circles. Such scanning may be performed up or down the sidewall to inspect, coat, grind, brush, wipe, spray or jet clean the sidewall or select portion thereof when the tank requires cleaning, inspection or maintenance. In certain instances, the operating head may have one or more grinding, welding, drilling or riveting tools operable under computer control to repair or construct select portions of the cylindrical side and bottom (or top) walls of the tank. Other embodiments of the operating head may be employed to inspect and repair select portions of the tank walls and/or to spray or extrusion coat all or select parts of the inside surfaces of the tank walls with plastic or other lining material. In another embodiment or method, the manipulator may be computer controlled to handle and fasten construction material(s) such as accurately shaped panels, together to automatically construct the same tank it is intended to maintain and clean, without the expenditure of human labor.
The manipulator may be centrally supported or mounted within the tank or reactor and secured therein, or it may be overhead supported above an opening in the tank and operated in a suspended condition. In the former case, the laterally extending manipulator arm or articulated arm assembly is mounted on an axially disposed rotor assembly either anchored centrally to the bottom wall or floor of the tank or reactor or secured to a fitting held in or against the bottom wall. The overhead carriage may travel on a monorail or dual rail conveyor such as a bridge crane which may operate to dispose such manipulator in selected ones of a plurality of tanks under computer control. In both embodiments, the rotor assembly is rotated to thereby cause the operating head of the manipulator to scan close to or contact the cylindrical surface of revolution defining a side wall of the tank.
In an embodiment where the manipulator is suspended overhead, the manipulator comprises a rotor assembly rotatably mounted on an overhead carriage. A vertically extending section of the rotor assembly oriented downward into the tank supports a laterally extending manipulator arm or assembly of articulated arms. The overhead carriage may be supported for two directional movement along an overhead monorail or dual rail system as well as by a bridge crane enabling lateral positioning of the carriage above a selected tank. The manipulator may be automatically operated to perform the described functions with respect to a plurality of storage and processing tanks and/or reactors disposed next to each other in one or more rows. If such tanks are open, the manipulator may be predeterminately aligned above the tank and the extendable section of the rotor assembly lowered therein. The manipulator arm assembly may then be power rotated about the central axis of the tank to cause its operating head to coat, brush, and/or spray or jet clean the cylindrical surface of the side wall of the tank in parallel-circular movements and/or helical scanning movements. For such cleaning, repair, or inspection of the flat bottom wall of the tank, the manipulator arm may also be pivoted with respect to the extendable section. The manipulator arm is then automatically driven to the bottom, and the operating head or heads thereof made to scan a select area or areas of the bottom wall of the tank or to scan and operate on the entire surface thereof in concentric circular or spiral bath scanning under computer control.
Other objects, features, and advantages of the invention will become evident in light of the following detailed description considered in conjunction with the referenced drawings of a preferred exemplary embodiment according to the present invention.